Rotary limit switch assembly



y 3, 1956 P. H. DANLY ET AL 2,753,405

ROTARY LIMIT SWITCH ASSEMBLY Filed June 30, 1953 3 Sheets-Sheet l /0 fo6 55 H 5 INVENTORS July 3, 1956 p, H. DANLY ET AL 2,753,405

ROTARY LIMIT SWITCH ASSEMBLY Filed June 30, 1953 3 Sheets-Sheet 2INVENTORS PH/LO H. DAM/LY 8c l fls/L GEOQGEFF MLW United States PatentROTARY LIMIT SWITCH ASSEMBLY Philo H. Danly, Hinsdale, and VasilGeorgefi, La Grange Park, Ill., assignors to Danly Machine Specialties,Inc., Chicago, 111., a corporation of Illinois Application June 30,1953, Serial No. 365,107 8 Claims. (Cl. 200-17) Our invention relates torotary limit switch assemblies and more particularly to an improvedrotary limit switch assembly wherein the positions of the switches maybe adjusted when the machine with which the assembly is used is inoperation.

In modern automatic machines many operations must be performed in theproper timed sequence, and some means must be provided for initiatingthe various operations in predetermined phase relation with the cycle ofthe machine. A machine requiring such a variety of operations is a powerpress. Some of the operations which must be automatically performed are,for example, stopping the press at the top of the stroke, the operationof mechanical handling devices, initiation of the feeding and removal ofmaterial, the operation of die stops, the supplying of drawing compoundto the stock and the operation of the locking device for the presscushion. The means used in the prior art to control these operations isa limit switch assembly. In these assemblies of the rotary type, aseries of radially spaced cams arranged on a shaft connected to thepress shaft actuate at the proper time each of a series of switchesfixedly mounted on the assembly housing. To set up the press, the camsare arranged in the estimated proper angular relationship on the shaft,the press is started and the operations ensue in approximately theproper relation. However, only in an extremely rare case will the camsbe properly positioned upon the first Setting. The sequence ofoperations after the first setting must be observed, the machine stoppedand the cams readjusted. That is, the proper setup of the press can onlybe determined by a series of trial and error operations, for each ofwhich operations the press must be stopped and restarted. To obviatethis necessity for continual stopping and starting, it has beensuggested that a linear limit switch assembly be used so that adjustmentof the switch positions is possible while the press is in motion. Insuch an assembly a cam member actuated from the press is reciprocatedalong a line with simple harmonic motion, and a number of switches areadjustably arranged alongside the cam in the proper spaced relationshipso as to be actuated at the proper times. It is well known, however,that in simple harmonic motion, the amplitude of motion is extremelysmall during certain intervals of the cycle. For example, between 3-00to 30 degrees in the cycle and from 150 to 210 degrees, approximately,the amplitude of displacement is very small in comparison with theamplitude in other intervals of the cycle. Therefore, if switches are soarranged alongside a linearly reciprocating cam member and a largenumber of operations required during one of the intervals referred toabove, a great number of switches must be crowded in a small space,since the cam moves only a small distance along the line in theinterval. If the number of operations required in an interval of smallamplitude of motion is great enough, it may well be physicallyimpossible to mount enough switches in the interval. Furthermore, inpresses in which limit switch assemblies are used to control the pressoperations during a working cycle, the stopping of the press is underthe control of one of the limit switches. Therefore, in the event thatthe drive means of the assembly is arrested by the rupture ordisengagement of its connection to the rotating press parts, the presswiL not be stopped by its limit switch but will continue to operateuntil stopped by the operator. During this continued period of operationthere is great danger of injury to the operator and to the press anddies. We have invented an improved rotary limit switch assembly whichpermits adjustment of the switches relative to the cams while the pressis in motion and provides equal space for switches in all intervals ofthe cycle, In addition we provide an improved rotary limit switchassembly including safety means for automatically stopping the presswhen the shaft of our rotary limit switch assembly is accidentallyarrested during an operating cycle.

One object of our invention is to provide an improved rotary limitswitch assembly wherein adjustment of the sequence of operations ispossible while the press is in motion.

Another object of our invention is the provision of an improved rotarylimit switch assembly wherein the results of any switch setting may beimmediately observed and corrected.

Another object of our invention is the provision of an improved rotarylimit switch assembly including means for automatically stopping thepress when the drive means of the assembly is arrested.

Other and further objects of our invention will appear from thefollowing description.

In general our invention contemplates the provision of a housing havinga shaft rotatably mounted therein, a plurality of cams mounted on theshaft and means for clamping said cams to the shaft in predeterminedangular relationship. A number of switches corresponding to the numberof operations it is desired to perform are provided for cooperation withrespective cams. Mounting means mount the cams for limited movement withrespect to the housing and locking means lock the switches in thepositions to which they have been moved. In addition we provide anembodiment including stop means for automatically stopping the presswhen the shaft of the switch assembly is arrested.

In the accompanying drawings which form part of the instantspecification and which are to be read in conjunction therewith and inwhich like reference numerals are used to indicate like parts in thevarious views:

Figure l is a perspective view of our improved rotary limit switchassembly showing the general arrangement of parts.

Figure 2 is a sectional view of the erally along the line 2-2 of Figurelarged scale.

Figure 3 is a sectional view along the line 3-3 of Figure 2.

Figure 4 is a fragmentary sectional view of another assembly taken gen-1, drawn on an enof the assembly taken embodiment of our invention.

Figure 5 is a sectional view with a part broken away taken along theline 5-5 of Figure 4.

More particularly, referring now to the drawings, we provide a housinggenerally indicated at 10 and having top and bottom members 11 and sides13 in which is rotatably mounted a shaft 12. One end of shaft 12 ismounted for rotation in a bearing 14 provided in one of the sides 13 ofhousing 10 and the other end of shaft 12 is supported in ball bearings16 mounted in the other side of housing 11). Bearing 16 is mounted in abearing housing 18 and retained therein by an annular plate 20 fixed tothe bearing cap by screws 22, and bearing housing 18 C) is secured to ahousing by suitable means such as screws 19. A shock absorbing washer 24is provided between the lip of housing 18 and the side of housing 10.Shaft 12 has an enlarged central portion 25 which may be of any desiredcross-sectional shape but is preferably in the form of a square havingrounded corners, as can readily be seen in Figure 3. It is desirablethat this portion 25 be of any such noncircular configuration in orderthat the friction between portion 25 and the members mounted thereon maybe a minimum, and a generally square section has been shown. One end ofshaft 12 is provided with a keyway 23 by means of which it is coupled tothe press drive so as to be rotated in phase therewith.

On the noncircular portion 25 of shaft 12 we mount a series of annularbushings 26, and between each pair of these bushings we arrange a pairof cam members 28 having circular openings therein to permit mountingthem on the shaft. Each bushing 26 mounts a pair of switch-supportingarms 30 and an annular spacer 32. It will be noted that each pair ofarms 30 is se arated by a washer 34, and washers 36 are disposed betweeneach pair of cams 28. In addition, alternate cams are spaced from theadjacent bushings by washers 38. We provide shaft 12 with threadedportions 40 and 42 at the ends of portion 25. An internally threadedsleeve or nut 44 is threaded on portion 40 and an internally recessednut 46 is threaded on portion 42. A spring 48 is disposed in the recess50 of nut 46 and bears on a washer 52 which in turn engages one of thebushings 26.

When We tighten nut 46 by means of a tool inserted in recess 54, theforce exerted is transmitted through washer 52 and bushing 26 to thecams and so forth through all the bushings and cams to sleeve 44. Thusthe cams are clamped between sleeve 44, the intervening bushings 26 andnut 46, and are thus rigidly held with respect to shaft 12 andconstrained to rotate therewith. When we desire to adjust the cams, weloosen nut 46 sufliciently to unclamp the cams. The spring 48 thenfrictionally holds the cams in position. The arms 30 are free to rotatewith respect to shaft 12, since they are not subjected to clampingpressure, being mounted on the bushings 26, while cams 28 rotate withthe shaft.

On the ends of the levers 30 we mount switches, generally indicated at56. As shown in the drawings, only certain of the arms 30 may haveswitches mounted thereon. The number of switches depends upon the numberof operations we desire to control. The switches are held on the leversby means of screws 58 pasing through arms 30 and into the switchhousings 60.

The switch housings 60 are made of insulating material and provided witha pair of recesses 62 for the reception of a pair of spring-urgedplungers 64 and 66. Plunger 64 may, for example, operate to close theswitch and plunger 66 to open the switch. Another opening 68 is providedin the housings to receive cam member 70, which is mounted on a shaft 72extending through member 70 and into a bushing 74 provided in a hole 76adjacent the end of arm 30. The opposite end of shaft 72 has a reducedportion 78 extending outside housing 60 and on which We fixedly mount anactuating arm 80 by means of a nut 82. On the other end of the arm 80 wemount a roller 84 for engagement with the cam 28 corresponding to thesupporting arm 30 on which the respective switch is mounted. Roller 84is carried by a bushing 86 surrounding a pin 88 having an enlargedportion 90 on one end for retaining the roller and a reduced portion 92on the other end, by means of which it is fixed on arm 80 by a nut 94.

We provide curved top and bottom members 11 of housing 10 with a seriesof spaced slots 98 in which we mount locking means, generally indicatedat 96. Each of the locking means includes a cylindrical locking pin 100,one end of which is of a reduced diameter and adapted to be inserted inthe recess 102 of a switch housing 60. Portions 104 of pins 100 arelaterally reduced in the di-:

rection of the width of slots 98 but not in the direction of the lengthof slots 98 so that pins ride along the slots but are prevented fromrotating in the slots. Pointers 106 and knurled locking nuts 108 aremounted on cylindrical threaded portions 110 extending above portion104. When the pins 100 are drawn up into the clamped position, no pullis exerted on the switch housing since the pins 100 slide relative torecesses 102. In addition, we have arranged the parts so that pin 100will not extend all the way within the recess 102 when the locking nut108 is clamped to the housing. Enough space is left so that pin 100 maydrop further into the recess 102 when the locking nut 108 is loosened.The pointers 106 are provided for cooperation with appropriate scales onhousing 10 so that we may record the relative ositions of the lockingmeans and associated switches in a particular operation.

We arrange certain of the switches at the top of the housing and certainothers at the bottom thereof. Generally alternate switches are at thetop and bottom of the housing, an arrangement dictated by spaceconsiderations. We can arrange the cams, of course, in any desiredangular relationship. Leads 112 extend from the switches to the outsideapparatus through an appropriately insulated opening 114 and are ofsufficient length to per mit adjustment of the position of the switchlever with which they are associated.

In the embodiment of our invention illustrated in Figures 4 and 5 wehave provided a simplified arrangement of parts and a safety means forstopping the press in the event that the shaft of the limit switchassembly is arrested by the rupture or disengagement of its connectionto the rotating press parts. In this form we mount a shaft having anenlarged central portion 122 of a noncircular configuration within thehousing 10. The right-hand end of this shaft is mounted in a bearing(not shown) similar to bearing 14 described in connection with theembodiment illustrated in Figures 1 and 2. The left-hand end of shaft120 is mounted in ball bearing 124. A collar 126 having an annularflange 128 on its inner periphery is fixed to housing 10 by anyappropriate means such as screws 130 and surrounds and seats the outerrace 132 of bearing 124. A nut 134 is threaded on shaft 120 and bears onthe inner race 136 of bearing 124 through a washer 138 to hold the innerrace in position against bushing 139 on the shaft. A bearing cap 140covers nut 134 and is fixed to collar 128 by any suitable means such asscrews 142. Cap 140 holds outer race 132 against flange 128.

We arrange a plurality of annular bushings 144 along the enlargedportion 122 of shaft 120. Between each pair of bushings 144, we disposea cam 146 having a circular opening 148 surrounding portion 122 of shaft120. Each bushing 144 carries a switch-supporting arm 150. A nut orcollar 152 is threaded on shaft 120 at the left-hand end of portion 122as viewed in Figure 4. Clamping means similar to that described inconnection with the embodiment illustrated in Figures 1 and 2 isprovided at the right-hand end of portion 122 to clamp the cams and armsin the selected relative positions around shaft 120.

Each of the arms is provided at a point intermediate its length with apair of spaced lateral projections 154 on which we mount a limit switch156 having an actuating button 158 by any suitable means such as screws160. Leads 159 and 161 provide electrical connections for the switch.

An arm 162 is pivotally mounted on a pin 164 carried by the arm 150.Each of the arms 162 has a roller 166 rotatably carried by a pin 168 onthe end of the arm 162 opposite pin 164. A recess 170 in each of thearms 162 houses a spring 172 which bears with one end on one of theprojections 154. Spring 172 urges arm 162 in a clockwise direction asviewed in Figure 5. A stop 173 on supporting arm 150 limits the movementof actuating arm 162 in this direction. We also provide each of the arms162 with a projection 174 for engagement with 'actuating button 158 ofthe associated limit switch 156. Each of the rollers 166 is so disposedas to be engaged by one of the cams 146 at some point in a cycle ofoperation of the switch. When a roller is engaged by a cam, therespective arm 162 is rotated in a counterclockwise direction as viewedin Figure 5 to engage its associated switch actuating button 158. Thearrangement of parts is such that springs 170 urge arms 162 to aposition where they bear against stops 173 and projections 174 will notactuate switch operating buttons 158 when the associated roller 166 isnot engaged by its respective cam.

Each of the arms 150 has a lateral flange 176 at its end. Locking means,generally indicated by reference character 178, are mounted in the slots98 in the curved top and bottom members 11 of housing 10. The lockingpins 180 of the assembly are adapted to be inserted in correspondingholes 182 in flanges 176 and have reduced portions 184' which ride inthe slots 98 and prevent rotation of pins 180. A knurled nut 186 andlock nut 188 are threaded on a shank 190 extending outwardly fromreduced portion 184 of each of the locking means 178. Suitable covers192, supported on hinges 194 fixed to housing by screws 196, may beprovided and held in the closed position by screws 198 carried by aflange 200 on the housing.

We key a collar 202 to shaft 120 at a point to the left of nut 152 asviewed in Figure 4 by means of a key 204. A spur gear 206 is attached toflange 208 of collar 202 by suitable means such as bolts 210. Gear 206drives a pinion 212 on the end of a coupling sleeve 214 fixed to theshaft 216 of a zero speed switch 220, of a type well known in the art,by means such as a set screw 215. Zero speed switch 220 is carried by ahousing 222 fixed to the housing 10 by suitable means such as screws224. An enclosure 226 mounted on the housing 10 by rivets 228 may beprovided to isolate gearing 206, 212 from the remainder of the switchassembly.

While we have shown the switches of our assembly supported on armscarried by the assembly shaft, it will be understood that the switchescould be mounted in the slots 98 and actuated by their respective camswith out the necessity of using any supporting arms. We prefer, however,to employ such supporting arms to hold the switches securely in thepositions in which they have been locked.

In operation, in the form of our invention shown in Figures l to 3, wefirst assemble our device in the manner shown with a suitable number ofswitches Within the housing and loosen nut 46 by means of a toolinserted in recess 54 to permit movement of cams 28 against frictionexerted by spring 48. Switch supporting arms are best positionedinitially in the center of slots 98 and clamped in position. We thendispose cams 28 in approximately the correct angular positions andtighten nut 46 so that it clamps the cams in the positions to which theyhave been moved. We start the press and observe the sequence ofoperations; invariably, adjustments must be made. To make adjustments,we loosen nuts 108 to permit movement of their associated switch and armalong a slot 98. When the proper positions have been reached, we againtighten the nut. The correct positions are determined during the timethe adjustment is being made by observation of the press operation. Whenall necessary adjustments have been made, the press will be operatingproperly and all functions will be performed in the desired sequence.That is, the cams 28 rotate and engage rollers 84 to rock actuating arms80 and rotate cam members 70 in the proper direction to actuate eitherplunger 64 or 66 to start or stop the equipment being controlled. Itshould be noted that we make all adjustments without the necessity ofstopping the press.

The operation of the embodiment illustrated in Figures 4 and 5 issimilar to that of the form shown in Figures 1 and 2. Locking means 178,carrying their associated arms 150 and switches 156, are moved to thecenters of slots 98 and locked. Cams 146 are moved to approximately thecorrect relative positions and clamped in place by the clamping means.The press is started and any necessary adjustments made by again movinglocking means 178 and their associated switches along the slots 98. Asis the case in the form illustrated in Figures 1 and 2, these lastadjustments can be made without stopping the press. When the switcheshave been set, the cams 146 rotate and engage their respective rollers166 to rotate arms 162 so that projections 174 actuate theircorresponding switch operating buttons 158 to perform the desiredoperations in the proper sequence.

In the event that the control shaft leading to shaft breaks or shaft 120for any reason ceases to rotate during a press cycle, spur gear 206 willno longer rotate pinion 212 and shaft 216 of the zero speed switch 220will stop. As is well known in the art, while shaft 216 of zero speedswitch 220 continues to rotate, the zero switch will be closed. However,when the shaft 216 stops, the switch will open. We have arranged ourdevice so that the opening of switch 220 will actuate the press controlto stop the press. Therefore, if for any reason shaft 120 stopsrotating, the press will be stopped.

Thus it will be seen that we have accomplished the objects of ourinvention. We have provided an improved rotary limit switch assemblywherein the results of the initial setting can be immediately observedand corrected without the'necessity of stopping the press. The trial anderror system of setting up a press has been eliminated. Only one settingup of the cams is necessary, and adjustments of the switches can be madeto achieve the desired operation without stopping the press even once.In addition, we have provided safety means for automatically stoppingthe press in the event that the shaft of the rotary limit switch for anyreason is arrested so that the press is not stopped by the proper limitswitch.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations. This is contemplated by and is within the scope of ourclaims. It is further obvious that various changes may be made indetails within the scope of our claims without departing from the spiritof our invention. It is therefore to be understood that our invention isnot to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. A rotary limit switch assembly comprising in combination a housing, ashaft rotatably mounted therein, a plurality of cams, means mountingsaid cams on said shaft for continuous adjustment of the circumferentialposition thereof on the shaft, means for clamping said cams to saidshaft in predetermined angular relationship for rotation therewith, aplurality of switches, means for adjustably mounting the switches onsaid shaft for movement with respect to the housing when said cams areclamped and locking means for locking respective switches in the desiredpositions with relation to said housing, said clamping means beingreleasable to permit adjustment of the circumferential position of saidcams while mounted on said shaft.

2. A rotary limit switch assembly as in claim 1 in which each of saidswitch mounting means comprises a bushing carried by the shaft and asupporting arm mounted on said bushing.

3. A rotary limit switch assembly as in claim 1 wherein said shaft isprovided with threaded portions adjacent its ends and said clampingmeans includes a plurality of bushings mounted on said shaftintermediate the threaded portions and arranged so as to bear againstsaid cams, a sleeve threadably mounted on one of said threaded portions,a nut mounted on the other of said threaded portions, the constructionbeing such as to exert clamping pressure on said cams through the mediumof said bushings when the nut is tightened. a. v

4. A rotary limit switch assembly as in claim 1 .in which said shaft isprovided with threaded portions, adjacent itsends and saidclamping meansincludes atplurality of bushings mounted on said shaft intermediate thethreaded portions and arranged so as to bear against said earns, asleeve threadably mounted on one of said threaded portions, a recessednut mounted on the other of said threaded portions and a spring disposedin the recess of said nut so as to exert frictional pressure on saidcams through the medium of said bushings.

5. A rotary limit switch assembly :as in claim 1 in which said housingincludes curved top and bottom .members provided with spaced slots andsaid locking means includesmernbers slidably mounted in said slots andmeans for locking said slidable members in the desired position in saidslots.

'6. A rotary limit switch assembly as in claim 1 wherein said switchmounting means includes a plurality of supporting arms mounted on saidshaft and said locking means includes members adjustably mounted on saidhousing, the arrangement of parts being such that pairs of said armsalternate with pairs of said cams along the shaft, and said adjustablymounted members are alternately mounted on the top and bottom of saidhousing.

7. A rotary limit switch assembly for use with a .machine tool includingin combination a housing, a shaft rotatably mounted therein, a pluralityof .cams, means mounting said cams on said shaft for continuousadjustment of the circumferential position thereof on the shaft, meansfor clamping said cams to said shaft in predetermined angularrelationship for rotation therewith, a plurality of switches, means foradjustably mounting the switches on said shaft for movement withrespectto the housing when said cams are clamped, locking means for lockingrespective switches in the desired position with relation to the housingand stop means operable to stop said tool when said shaft is arrested,said clamping means being releasable to permit adjustment of thecircumferential position of said cams while mounted on said shaft.

8. A rotary limit switch assembly for use with a machine ttool includingin combination a housing, a shaft rotatably mounted in the housing, aplurality of cams, means mounting said cams on the shaft for continuousadjustment of the circumferential position thereof on the shaft, meansfor clamping said cams to said shaft in predetermined angularrelationship for rotation therewith, a plurality of switches, means foradjustably mounting the switches on said shaft for movement with respectto the housing when said cams are clamped, locking means for lockingrespective switches in the desired position with respect to saidhousing, a zero speed switch and means for driving said zero speedswitch from said shaft whereby said zero speed switch will stop themachine tool when said shaft is arrested, said clamping means beingreleasable to permit adjustment of the circumferential position of saidcams while mounted on said shaft.

References Cited in the file of this patent UNITED STATES PATENTS2,169,039 Defandorf et al. Aug. 8, 1939 2,202,698 Latta May 28, 19402,273,963 Jereczek Feb. 24, 1942 2,636,949 Hunter Apr. 28, 1953

